300 
Records for this species which have accumu- 
lated since the original description, in addition 
to those for the allotype, are as follows. 
Cotorapo. — Estes, Mill Creek: June 11, 
1937, 01a O8 
OREGON.—OcHoco CREEK: May 3, 1939, 19. 
Uran.—Bic Corronwoops Canyon: April 
24, 1937, G. F. Knowlton & F. C. Harmston, 
192. Locan Canyon: June 18, 1937, Knowl- 
ton & Nye, 12; April 23, 1938, W. P. Nye, 
14,19; April 19, 1940, R. E. Nye, aa O. 
East of DANIELS: June 4, 1940, Knowlton & 
Vansell, 19. 
The above specimens confirm the state- 
ment made when the type, a specimen re- 
laxed from a pin mount, was described, 
that the submental gill as it occurs in 
Hydroperla and Perlodes is lacking. How- 
ever, there is a slight trace of a nipple- 
like projection at each outer posterior cor- 
ner of the submentum suggestive of an 
atrophied submental gill. A similar situa- 
tion is found in the case of Diploperla 
hastata (Banks) from 
America and other species of Diploperla. 
I now believe that the genus Dictyoptery- 
gella, including knowltonti, should be 
placed in the family Perlodidae, which is 
NyMPHAL 
MANDIBLES 
X53) J 
NYMPHAL LABIUM 
NyYMPHAL 
MAXILLA 
Mi é 
ue | 
UAT 
9 SUBGENITAL 
PLATE 
jUTUwuil | 
Fig. 72.—Dictyopterygella knowltoni. 
Ittinois NaturAL History SURVEY BULLETIN 
eastern North 
Vol. 22, Arteg 
the family where this genus has been 
placed by recent European authors. 
The thoracic cervical sternites of knowl- 
toni, and various species of Perlodes, 
Fig. 73.—Nymph of Dictyopterygella 
knowltoni. 
Hydroperla and Perla, possess weakly scle- 
rotized folds or bulbous areas which prob- 
ably play a part in respiration. 
In the original description of the male 
of knowltoni (Frison 1937), an error 0c 
curs in regard to comparative lengths of 
tarsal segments. “This statement should 
read: first and second tarsal segments t0- 
gether about one-half as long as third, first 
tarsal segment longer than the second. 
Among a lot of stonefly specimens lent 
to Dr. W. E. Ricker by the Canadian 
National Collection, Ottawa, Canada, and 
subsequently sent me for examination, are 
nymphs, adult females and an exuvia 
